Substrate is a whole can of worms unto itself
I use Indented Kraft paper becuase in my rack system, I don't have to worry about my subtrate keeping my humidity up.
Way back when I still used a glass tanks, I used the shredded coconut stuff for a while and then tried Eco Earth. Ultimatly, humidity troubles are why I ditched the glass tanks and went to PVC cages. Once I went over 4 snakes, I switched to racks and tubs. I haven't looked back since.
A lot of folks have more recent glass tank experience than I do. I'm sure some one will pipe in with a suggestion.